Gauging device for surface grinder



June 26, 1956 H. F. SKILLINGS GAUGING DEVICE FOR SURFACE GRINDER 6 Sheets-Sheet 1 Filed July 14. 1951 June 26, 1956 H. F. SKlLLlNGS 2,751,722

GAUGING DEVICE FOR SURFACE GRINDER Filed July 14, 1951 6 Sheets-Sheet 2 esa June 26, 1956 H. F. SKILLINGS 2,751,722

GAUGING DEVICE FOR SURFACE GRINDER Filed July 14, 1951 6 Sheets-Sheet 3 Fig.6.

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June 26, I956 Filed July 14. 1951 H. F. SKILLINGS GAUGING DEVICE FOR SURFACE GRINDER 6 Sheets-Sheet 6 United States Patent GAUGING DEVICE FOR SURFACE GRINDER Harold F. Skillings, West Medford, Mass, assignor to The Blanchard Machine Company, Cambridge, Mass, a corporation of Massachusetts Application July 14, 1951, Serial No. 236,781

30 Claims. (Cl. 51-131) The invention relates to a gauging device for use with a surface grinding machine of the general type in which the work is supported on a fiat supporting face and is ground to a predetermined thickness by means of a grinding wheel adapted for relative traversing and depth feeding movements with relation to the work supporting surface.

The invention is herein more specifically illustrated as embodied in a surface grinding machine of the general type having a transversely movable carriage, a rotary magnetic work supporting chuck on the carriage, and a vertically movable grinding head with an end face grinding wheel rotatable about a vertical axis and adapted for rapid traverse movements and for feeding movement toward the work face. In machines of this type one or a plurality of workpieces may be mounted on the work supporting face of the chuck which is then given a rotary traversing movement to bring all portions of the work supporting face successively into grinding relation with the grinding wheel, which is, at the same time, advanced slowly against the work.

It will be understood that while the invention is illustrated in a preferred form as embodied in the standard type of surface grinder above described that certain features of the invention are broadly applicable to other types of surface grinder including, for example, surface grinders in which relative reciprocatory movements are imparted to the work support and grinding wheel for the performance of a surface grinding operation on one or a plurality of workpieces mounted thereon, sur face grinders in which a grinding wheel having a peripheral grinding surface is mounted on a horizontal axis for traversing movements along aradial line toward and away from the rotational axis of a rotatable work support or chuck, and automatic grinders of the general type shown, for example, in the U. S. patent to Spencer, No. 1,535,080, in which successive workpieces are ground to a predetermined size in a single pass beneath an end face grinding wheel and are then discharged from the machine.

The gauging and finishing to an exact size of any one or more workpieces which may be disposed about the face of the chuck is normally accomplished with the assistance of direct measurements made by the operator from time to time as the work is brought down to size. This is a manual operation requiring a high degree of skill and constant attention on the part of the operator. While there has been an increasing demand for a more automatic control of surface grinding operations, the very substantial difliculty has been encountered that gauging devices of ordinary description which bear against or are otherwise responsive to the position of the work surfaces about the chuck face, are affected also by the voids between the workpieces passing under the gauge, and are therefore not well adapted for use while the work supporting chuck is in operation to obtain accurate readings or indications of work size,

' is a p inc pa o jec of the nvent n o p o e, fo

2,751,722 Patented June 26, 1956 2 use in a surface grinding machine of the general type described in which a grinding operation is performed on one or a plurality of workpieces mounted on a flat work supporting surface, a gauging device which will operate in a novel and improved manner with relation to the intermittently spaced work surfaces during the progress of the grinding operation to indicate a definite work thickness within very close limits for use in connection with the further control of and stopping of the machine.

More specifically it is an object of the invention to provide a feeler type gauging device including a work engaging element together with supporting and actuating devices constructed and arranged to produce a gauging device of the greatest possible sensitivity and stability under the conditions imposed in the operation of a SUI-.- face grinder.

It is a further object of the invention to provide a gauging device particularly adapted for use in a surface grinding machine in which an intermittent response to the passage of a series of spaced oversize workpieces under the gauge is followed by a change in the character of the response produced as the ground surface or surfaces are brought down to the finish size and in which means are provided for utilizing this variation in the response produced to provide a useable indication for manual or power control of the machine.

Other objects of the invention relate to the provision of specific improvements of construction and arrangements of parts in a gauging device for use in a surface grinding machine as will hereinafter more fully appear.

In accordance with the invention a gauging device of the feeler type is provided which comprises a gauge support disposed over the rotating work face of a surface grinding machine, and a work engaging element pivotally mounted on the support and arranged to be moved yieldably toward the work until the work engaging element has reached a substantially perpendicular position with relation to a moving portion of the work supporting chuck face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face. The arrangement of the gauging device so that the work engaging element moves to a substantially vertically pendant limit stop position with relation to the ground surfaces of the work insures a high degree of sensitivity and of certainty in operation of the gauge for the reason that as the element approaches the vertical position an increment of movement of the element about its pivot which is sufficient to actuate a microswitch or other actuating element is accompanied by diminishing increments of downward movement of the work engaging element which are accurately measurable in very small units which may be to the nearest ten thousandths of an inch.

Another feature of the arrangement which contributes to the very fine sensitivity of the gauge consists in the arrangement of the pivoted work engaging element for movement along a path and in a direction opposed to the direction of movement of the work support in combination with the yieldable advancing means whereby the work engaging element is permitted to move arcuately out of position whenever the tip of the work engaging element moving downwardly into a void between the workpieces is engaged by an oversize workpiece passing beneath said element.

Further in accordance with the invention a novel cooperation is achieved between the work engaging element and the micro-switch, or other actuating element which may be provided, in order to determine the precise instant during the grinding operation at which the workpiece or pieces disposed about the chuck have been brought down to exactly the desired size. While the grinding operation proceeds, the work engaging element moving downwardly into the voids between the work surfaces being ground, will. intermittently engage and then be moved away from the actuating element, thus providing an intermittent response, which becomes steady as the work is brought down to its finish size and the work engaging element is thereby permitted to remain in its limit position. A visual signal is obtained to enable the operator to stop the grinding wheel feed manually when the work has been brought precisely to its desired size by means of an electrical lamp placed in a circuit with the limit stop micro-switch. A flickering of the lamp willindicate that the size of the work is approaching the finish depth. A change from a flickering to a steady light from the lamp indicates that the surfaces being ground have been brought down to the finish size and the grinding feed should, therefore, be arrested.

A feature of the invention consists in the provision of a means cooperating with the gauging device described for automatically arresting the power-operated grinding feed' of the machine on the indication given, as above described, of a change from an intermittent to a steady response by the actuating element of the gauging device. In the illustrated form of the invention the limit stop micro-switch referred to is arranged to close a circuit having in series with the micro-switch the actuating relay of a timing device which is adjusted to time out only after the Work supporting chuck has completed one full revolution. Intermittent operation of the micro-switch caused by the movement of the work engaging element downwardly into the voids between the work surfaces to close the switch, and followed by a reverse movement of said element away from the switch as the element is engaged with the still oversize workpiece, will cause the timing device relay to be de-energized before the device times out. The timing device is permitted to time out only after the chuck is rotated through a full revolution, thus indicating that any workpieces on the chuck passing beneath the work engaging element have been brought to the desired size.

Further in accordance with the invention a driving mechanism is provided which acts yieldably to advance the work engaging element against the work at a somewhat faster rate than the rate of stock removal. This arrangement consists of a synchronous motor which is connected through a friction driving device to impart a steady rotational urge to the work engaging element along its arcuate path against the limit stop. The rate of drive is adjusted so that the component of movement of the work engaging element downwardly against the work is always at a faster rate than the rate of stock removal. For the extremely accurate measurements required of the gauging device disclosed an extremely light and at the same time constant pressure is maintained in the frictional drive above referred to for advancing the work engaging element against the work surface. In the illustrated form of the device the frictional driving connection between the pivotally supported work engaging element and the driving motor is constructed and arranged 'to slip when a pressure in excess of two ounces is applied against the tip of the work engaging element in the arcuate direction. A constantly applied frictional resistance is provided by means of a pair of axially preloaded ball bearings on the work engaging element pivot shaft which engage between them a driving disc, the amount of the pressure applied being suflicient to produce a slight distortion and a small but predictable resistance within the two bearings.

The invention will be best understood by reference to the following description taken in connection with the accompanying drawings, in which Fig. 1 is a sectional view in elevation of the work gauging device for a surface grinding machine in accordance with the present invention illustrating the gauge post mounted on the work chuck supporting carriage of the machine, a horizontally disposed gauge arm supported from the post, a gauge unit housing with the cover removed, and a work engaging element projecting downwardly from the further end of the housing against the work; i

Fig. 2 is a diagrammatic plan view of the work carriage and rotary chuck shown in alternative loading and operating positions with relation to the rotatable end face grinding wheel;

Fig. 3 is an enlarged detail view of the gauge unit illustrated in Fig. 1 with the cover removed and with portions of the casing wall sectioned;

Fig. 4 is a sectional view taken on a line 44 of Fig 3;

Fig. 5 is a general view in front elevation of a surface grinding machine provided with a work gauging device adapted for automatic control of the machine including the sizing of the work in accordance with certain features of the invention;

Fig. 6 is a detail sectional view taken on a line 66 of Fig. 7 illustrating particularly the solenoid actuated mechanism for disengaging the grinding wheel feed pawl to arrest the grinding wheel feed;

Fig. 7 is a partial view looking from the rear of the upper gear box of the machine enclosing the pawl and ratchet mechanism for effecting a power feed of the grinding wheel together with the solenoid operated controls for slowing and stopping of the grinding wheel feed;

Fig. 8 is a detail sectional view of the friction driving connection for the work engaging element as shown in Fig. 4 but on a larger scale; 7

Fig. 9 is an electrical diagram illustrating the electrical connections employed in connection with the work gauging device of the present invention for controlling the operation of the grinding wheel feed, only such portions of the electrical system of the machine being shown which are believed necessary to illustrate the connection of the present invention therewith;

Fig. 10 is adetail view illustrating an alternative. form of slow grinding feed control having a slow feed timer;

Fig. 11 is a view similar to Fig. 3 of the gauge housing, but illustrating a modified form of the invention in which the work engaging element is continuously urged toward a limiting depth position by means of a spring, and a signal lamp is employed to indicate the grinding of separated workpieces on the work supporting chuck to the desired size; and

Fig. 12 is a view similar to Figs. 3 and 11 but illustrating another embodiment of the invention in which a dash pot is provided for causing a spring actuated work engaging element to be moved toward the work at a controlled rate.

The invention is herein disclosed as embodied in a surface grinding machine having a rotary work support in the form of a magnetic chuck 46 which is rotatably supported on a carriage 47 movable between an operative position indicated in full lines in Fig. 2 with relation to an end face grinding wheel 48 and an alternative loading position indicated in dotted lines in Fig. 2. As indicated in the general view, Fig. 5, the surface grinding machine may consist of a base 49 having horizontally disposed ways, not specifically shown, on which the carriage 47 is movable from one to the other of the two positions indicated in Fig. 2, and a vertically disposed column 50 having ways 51 on which is mounted a grinding head 52 for movements downwardly against the face of the chuck 46 to bring the grinding wheel into grinding contact with any one or more workpieces which may be mounted on the rotary work support or chuck 46. As best shown in Fig. 5, the grinding wheel 48 mounted on the lower end of a vertical shaft 54, is supported from the grind ing head 52, and is arranged to be continuously driven by means of an electric motor in the head 52.

Further as indicated in Fig. 5 power operated mechanisms are provided for imparting rotational movements to the work supporting chuck 46 and a stepped feeding movement to the grinding head against the work. ,While such mechanism is well known in the art as shown, for

example, in the patent to Spencer, No. 1,553,084.),v these;

connections will be briefly described in connection with Figs. 5 and 6 of the drawings as follows: Power is taken from a feed motor 56 through an input connection 58 toa lower gear box 60 carried on the machine base. Rotary movements are imparted from the. variable speed gearing in the gear box 60 through a telescoping drive shaft 62, a bevel gear 64 on the shaft, a meshing bevel gear 66 on a short vertically disposed shaft 68'assembled in a bearing 69 on the carriage 47, and a pinion 70 on the shaft 68 which meshes with a gear 72 formed integrally with the rotary work supporting chuck 46. As further indicated in Fig. 5, adjustment of the variable speed gearing in the gear box 60 is effected by the operator through the adjustment of a manually operable control lever 73.

Stepped feeding movements imparted to the grinding head 52 with the grinding wheel 48 toward the work supporting face of the chuck 46 through connections which includes a conventional vertically disposed screw 74 carried by the column 50 and a nut 76 which is formed integrally with the grinding head 52. Rotational movements are imparted to the screw 74 by means of a worm gear 78 formed integrally with the screw 74, and a worm 80 which is carried on a horizontally disposed feed screw drive shaft 82 located within an upper gear box 84 on the machine column 50. For power operation of the grinding head feed screw shaft 82 at a quick traverse rate, a head traverse motor generally indicated at 302 in the electrical diagram, Fig. 9, is provided connected through suitable gearing, not illustrated, with the worm shaft 82. For power operation of the grinding head feed screw shaft 82 at a feeding rate, there is provided a conventional pawl and ratchet mechanism which comprises a ratchet wheel 86 loosely mounted to turn on a supporting shaft 88, and a cooperating pawl 98. The ratchet wheel 86 is connected to drive the feed screw drive shaft 82 through connections which include a gear 90 formed on the sleeve hub of the ratchet wheel 86, idler gears 92, 94, and a gear 96 secured to the feed screw drive shaft 82. The actuating pawl 98 for the ratchet wheel is pivoted on a pin 100 on a horizontally extending arm of a pawl lever 102 which is loosely sleeved to turn on the supporting shaft 88. A continuous reciprocatory movement is imparted to the pawl and pawl lever through connections from the lower feed box 60 comprising a telescoping drive shaft 104 which extends upwardly from the lower gear box 60 and at its upper end, see Fig. 7, carries a worm 106 for engagement with a worm gear 108 integral with a disc 110 and a feed pawl actuating crank pin 112. The pawl 98 is driven from the crank pin 112 by means of a link 114 which is connected at its upper end to the pawl pivot pin 100 and at its lower end is formed with a slot 116 which engages the crank pin 112. With the construction shown the rate of the feeding movement is controlled by limiting the downward or recovery movement of the pawl 98. For manually adjusting the extent of the stepped feeding movement imparted to the ratchet wheel 86, a horizontally disposed rack bar 118 is provided (see Fig. 7) which is connected at one end by means of a pinion 120 with a manually operable adjusting device generally indicated at 122, and at its other end is provided with a stop plate 124 disposed in the path of movement of an upwardly extending arm 126 of pawl lever 102.

With the illustrated construction a further slow feed control is provided for the pawl and ratchet feed which is adapted to be operated automatically by the work gauging device to reduce the grinding feed to a predetermined slow rate when the work has been reduced nearly to its finished size. The slow feed control referred to, as best shown in Fig. 7, comprises a block 128 which is supported to turn about a stationary pivot 130 and is connected at one end by means of a pin 134 and a link 136 with the armature 138 of a solenoid 140. When the solenoid is energized, the armature 138' moves upwardly, causing the black 128' to turn about the stajtionarypivot to the P s ion shown in g- 7 in whi h he free end: of the block 128 falls: behind a stop P n 142 carried; by-the,verti-. cal; arm 12 6 of the bell crank lever 102. The block 128 limits the recovery movement of the pawl 98. so that the pawl is etfective during each reciprocation thereof to ad-v vance the ratchet wheel by one tooth only, thus causing the grinding wheel to continue its feeding movement toward the work at a predetermined slow rate. The block 128 is formed with a slot to receive the pivot pin 130 so that in the event the solenoid is energized and the, block 128' is moved downwardly to its locking position when the pawl is retracted, the stop pin 142 during the subsequent clockwise feeding movement of the pawl and pawl lever may trip past the block 128 into its locking position. A iink 143 is connected between the, pivots, 130 and 134 in parallel relation to the block 128.

With the illustrated construction a novel additional stop feed control is provided for the pawl and ratchet feed mechanism which is adapted to be operated automatically by the work gauging device to disengage the pawl 98 from the ratchet wheel 86 and thereby to discontinue the further feeding movement of the grinding wheel when the work has been brought to size. The mechanism for dis engaging the pawl as shown in Figs. 6 and 7 comprises a pawl control arm 144 which is secured to turn as a unit with the pawl pivot pin 100 and pawl 98, and is formed at its free end with a ring portion which fits loosely around an extension 146 of the shaft 88. The, pawl control arm 144 is moved upwardly to a feed stop position in which the feed pawl 98 is out of engagement with the feed ratchet 86 by means of a horizontally disposed pawl throw-out lever 148 which is mounted to turn on the pivot 158 for idler gear 94 and at its free, end is arranged to engage beneath the ring portion forming the free end of pawl control arm 14.4. The pawl throw-out lever 148 is connected by a link 152 with one arm of a bell crank 154 in the form of two parallel triangular plates pivoted to turn about a fixed pivot 156. The bell crank 154 is connected by means of a horizontally disposed link 158 with a bell crank 160, which also takes the form of two parallel triangular plates. The other arm of the bell crank 160 is connected by a link 162 with an armature 164 of a solenoid 166. With this construction when the solenoid 166 is energized the armature and associated parts, including a pawl throw-out lever 148 will be raised, thus turning the pawl 98 about its pivot 100 out of contact with the ratchet 86.

The work gauging device provided in accordance with the invention for use in a surface grinding machine of the general type described comprises generally a gauge post 200 carried on an extension 201 of the carriage 47, a gauge arm 202 supported for adjustment vertically on the post, and a gauging unit comprising a housing 204 which is supported for a further fine adjustment vertically on gauge arm 202, and carries a depending work engaging element 206. The gauge post 200 is supported at its lower end for rotational adjustment in a preloaded roller hearing support 298 which is rigidly secured by bolts 209 to the carriage extension 201. A collar 210 fastened to the post 200 by means of a set screw 212 serves as a protective cover to prevent entry of chips into the bearing and is also equipped with a manually operable handle 214 for effecting a rotational adjustment of the post. The gauge arm 202 is formed with a sleeve hub 216 which is fitted for sliding and turning movement on the post, and rests upon and is secured to a nut element in the form of a ring 218 within which is supported a shoe 220 having a feather which engages in a spiral groove 222 in the post. Vertical adjustment of the gauge arm 202 may be readily effected by rotating the post 200 relatively to the gauge arrn 202 and nut element secured thereto. A tightening screw generally indicated at 224 serves to rigidly secure the gauge arm 202 in adjusted position with relation to thepost. A cylindrical cap 226 fitted over the top of the post and secured at its lower end to the sleeve hub 216 of the gauge arm serves to protect the spiral groove on the post from collecting dirt and chips.

The gauge unithousing 204 is mounted for fine vertical adjustment with relation to the gauge arm 202 on a vertically disposed supporting hollow pivot pin 228 tightly fitted into a socket 230 formed in the outer end of the gauge arm. The gauge unit housing 204 is formed with a sleeve hub 232 which is fitted onto the pivot pin 228. A key -234 fastened to the sleeve hub 232 and arranged to ride in' a slot 236 in the pivot pin 228 serves to prevent rotational movement while permitting a limited axial movement of the hub 232 and housing 204 on the post 230.;Vertical adjustment of the gauging unit housing 204 relative to the gauge arm 202 is effected by means of a micrometer screw 238 threaded toward its lower end into a nut 240 formed in the hollow pivot pin 228 and at its upper end rotatably and axially supported in a suitable bearing 241 formed in the upper end of the sleeve hub 232. A manual knob 242 is secured to the upper end of the screw 2.38. V

The gauging unit carried by the housing 204 in the preferred form of the invention illustrated in Figs. 1, 3, and 4 consists of the work engaging element 206 shown as a cylindrical rod which is slidably mounted in a bushing 246 carried in the enlarged end of a horizontally disposed shaft 248 rotatably supported in a plug 250 mounted in a wall of the housing 204. In order to eliminate so far as possible any friction losses, the shaft 248 is supported on two ball bearings 254, 255 within the plug 250, the outer races being held in position by a sleeve spacer 252. The'work engaging element 206 is supported yieldably in an extended position with relation to the bushing 246 as shown in Fig. 4 by means of a compression spring 256 seated atone end against a collar 258 on the work engaging element 206 and at its other end against the flanged end of the bushing 246.

The shaft 248 and work engaging element 206 are continuously yieldably driven or urged in a clockwise direction as viewed in Fig. 3 by means of a synchronous clock motor 260. Inasmuch as the clock mechanism referred to is of ordinary description, a detailed illustration or description thereof is believed unnecessary. The output shaft of the clock mechanism designated at 262 carries a pinion 264 which meshes with a friction driving gear 266 on the shaft 248. In order to maintain a light but at the same time constant unvaried frictional engagement of the friction driving gear 266 with shaft 248, the drive is taken through two axially preloaded ball bearings 268, 270 which are mounted on the shaft 248, one at each side of the frictiondriving gear 266. The two outer races of these bearings firmly engage between them the friction driving gear 266. The inner edge of the gear 266 is thinned so that the inner races of the bearings are out of contact therewith. The inner race of bearing 268 at its outer end bears against the flanged bushing 273 secured tothe shaft 248. Bellville springs 272 interposed between the inner race of ball bearing 270 and the inner race of ball bearing 254 act to preload the bearings axially, causing a slight amount of distortion so that a small frictional resistance is built up in the bearings which 'may be accurately determined and will remain constant for the life of the bearing. In the embodiment of the invention shown in Figs. 1, 3, and 4 the arrangement is such that a force of two ounces applied against the tip of the work engaging element in the direction of movement .will produce slippage between the friction driving gear 266 and shaft 248.

With the illustrated construction the shaft 248 and work'engaging element 206 are arranged to be moved from aretracted position which may be, for example, the dotted line position of Fig. 3 to the substantially verti- 'ca'l position with relation to the work face of the chuck 40shown in full lines in Fig. 3. Movement of these paiits'in'a reverse or upward direction is arrested by the engagement of a downwardly extendingsplit clamp type:

bracket 276 secured to the shaft 248 with a stop pin 278 screw-threaded for adjustment into the wall 'of the housi ing 204. Movement of the work engaging element 206, pivot shaft 248 and bracket in a forward downward,di.

rection is limited by engagement of the bracket 276 with.

and adjustable stop pin 279. 1

The work engaging element is rotatedby the syn. chr'onous motor to cause the contact point thereof, to be moved or to be urged downwardly against the work surface at a rate somewhat in excess of the rate of stock removal. .This condition of downward. pressure against the work is maintained as the work engaging element ap-' proaches its limit stop position even though the downward increment of movement is sharply decreased since the rate of feed of the grinding wheel is also sharply reduced at this time as hereinafter more fully set forth. The controlled advance of the work engaging element at a rate which is only slightly in excess of the rate of stock removal substantially reduces the possible swing'of the work engaging element below the level of the intermittently spaced ground work surfaces, contributes to the sensitivity and accuracy of the gauge, reduces the wear upon the electrical devices, and also makes possible a novel cooperation of the pivoted work engaging element with a control micro-switch for the performance of auxiliary operations during continued operation of the machine for stock removal, as exemplified by the shift to a low rate of feed for a finish grinding operation upon the work.

Movement of the'work engaging element 206 against the work to a position somewhat short of the final rest position causes a slow grinding feed micro-switch 280 to be operated to decrease the rate 'of feed of the grinding wheel to a predetermined slow feed rate. Subsequent movement of the Work engaging element toits final stop position of Fig. 3 causes a grinding feed stop micro-switch 282 to be operated to arrest the feeding movement of the grinding wheel. Micro-switch 280 is mounted on a spring plate 283 suspended from the left 'wall of the unit housing 204 as shown in Fig. 3, and may be moved to an adjusted position toward or away from the wall by means of an adjusting screw 284. Micro-switch 282 is rigidly secured to the right hand wall of the unit housing 204 as viewed in Fig. 3. For actuating the two micro-switches a switch contact arm 286 is provided which extends downwardly between the two micro-switches, being arranged to swingabout about a pivot 287 at its upper end and at its lower end arranged to be engaged by an upward extension 285 of the bracket 276 on the pivot shaftv 248. The arm 286 is normally allowed to swing to the left from the position shown in Fig. 3 under the influence 0f acompression spring 288 so that the arm is normally engaged with a contact element 290 forming part of the slow speed micro-switch 280 holding this switch in open position. Movement of the work engaging element 206 from the dotted line position in Fig., 3 to a point at which the extension 285 of bracket 276'thereof engages the corresponding surface on the depending arm 286 causes the arm to be moved to the right against the pressure of its spring 288 to release the contact element 290 on microswitch 280, permitting this switch to close. Continued movement of the work engaging element 206 and associated parts including rock shaft 248 and extension 285 to the limiting full line position in Fig. 3 will cause the arm 286 to be moved into engagement with a contact element 201 forming part of the micro-switch 282, causing this switch to close.

. A. feature of the invention consists in the combination of the work gauging device above described with the electrical control devices hereinafter described, which are rendered operative by the operation of the micro-switches 280 and 282 to slow and thereafter to stop the grinding feed as the work is ground down to the exactsize required.

, 9 The electrical devices'referred to wi1l'be des'cribed inconnection with theelectrical diagram, Fig. 9. 7

Power is supplied from a three-phase system including lines L1, L2, L3 through connectors T1, T2, T3, respectively, to an up rapid traverse switch 300 to drive the grinding head rapid traverse motor 302' and grinding head upwardly or alternatively through lead wires T4, Ts, Ts through a down rapid traverse switch 304 to drive the grinding head rapid traverse motor in the down direction. Power is also supplied from lines L1, L2 through lead wires Tr1 and Trz to a step-down transformer 306 for a low voltage circuit including an output wire 20 and a return wire 21 for the operation of the several control switches and relays in the electrical system.

When the work has been brought s'uificiently close to size so that the switch control arm 286 is actuated to permit the closing of micro-switch 280, a slow grinding feed solenoid circuit is closed which includes input wire 20, a lead wire 22, micro-switch 280, a lead wire 23, the slow grinding feed solenoid 140, a lead Wire 24, and the return wire 21. Solenoid 140 is energized, causing the armature 138 to be moved upwardly which, in turn, moves the block 128 into the path of movement of the pawl lever and feed pawl associated therewith which thereafter picks up only one tooth during each reciprocation. The grinding operation continues at the slow rate.

While the gauging device which forms the subject matter of the invention is in operation, it will be understood that the synchronous motor and friction drive above described tends to project the work engaging element 206 against the work at a faster rate than that at which stock is removed from the work surface. Where one or more individual workpieces are mounted on the chuck surface so that the work contact element encounters alternatively the ground surfaces and intervening voids, the work engaging element 206 will be driven somewhat below the level of the work surface being then brought back to a corrected position each time a ground surface passes beneath the work engaging element. Under the conditions described in which substantial voids exist, it may be expected that the work engaging element will be repeatedly driven to its limiting stop position in which the contact element 291 of the stop micro-switch 282 will be closed and thereafter permitted again to open as the position of the work engaging element is again corrected by engagement with the ground surface of the work. An intermittent closing and opening of the microswitch 282 takes place until the work reaches its final size whereupon the switch remains finally closed. This intermittent opening and closing followed by a final closing of the switch is utilized in accordance with the present invention to provide an accurate indication that the work mounted on the chuck has been ground to the exact size required, and is also employed to effect the automatic stopping of the work feed and the performance of such other aum'liary operations as may be desired.

The closing of the micro-switch 282 acts to close a stop feed timer circuit which includes the input wire 20, a lead wire 25, the feed limit micro-switch 282, a lead wire 26, a stop feed timer relay 308, a lead wire 27, and the return wire 21. A lamp 307 connected between the lead wire 27 and return wire 21 gives a visual indication for the benefit of the operator whenever the feed stop micro-switch 282 is closed. The feed stop timer referred to may be of ordinary description and is therefore shown in diagrammatic form only in Fig. 9 as including with the solenoid 308, an armature 309 to which is attached a dash pot 310 and a timer actuated switch 312. The length of time required for the timer to time out may be regulated by means of an exhaust connection from the dash pot, including a manually adjustable regulator 314. For the correct operation of the timing device in the illustrated construction, it is contemplated that the timer will be adjusted to time out after a period of time in which T0 the rotary: work supporting chuck' 46 willhave turned through slightly more than one complete revolution. For this purpose the regulator 314 will preferably be calibrated to correspond with the adjustment of the chuck change speed control: lever 73 shown in Fig. 5.

Assuming that the work engaging element 206, passing over one of the voids'between the workpieces, hasmoved to the limit stop position below the level of the ground surface of the work and is therefore moved in a reverse direction upon contact with the next ground surface, the micro-switch 232 closes and then opens to break the cir cuit to the timer relay 308 before the chuck will have rotated through one full revolution and before the timer will have timed out. Under these conditions the armature 309 is permitted to return to its initial starting position and the entire timing cycle is lost.

With this arrangement of the gauging and electrical control devices, the stop feed timer is permitted to time out only after the operation of the stop feed microswitch 282 has ceased to be intermittent and remains closed through at least one revolution of the grinding chuck 40. The closing of the timer switch 312 operates to energize a stop feed relay switch circuit which includes the output wire 20, a lead wire 28, a feed stop switch relay 316, a lead wire 29, the stop feed timer switch 312, a lead wire 30, and the return wire 21. At the same time an auxiliary circuit is closed to a dwell timer relay 318 through the output wire 20, a lead wire 34, relay 318, and a lead wire- 35' which will cause the head traverse motor up switch to be closed and the head traverse motor to be driven in an up direction to move the grinding head and grinding wheel from the work after a dwell period in which the grinding wheel is permitted to spark out.

The closing of the relay switch 317 closes a stop feed solenoid circuit through output wire 20, a lead wire 31,v the stop feed solenoid 166, lead wire 33, and return wire 21. Stop solenoid 166 is energized and acts through the connections above described, including pawl throw-- out lever 148 and pawl control arm 144 to shift the: feed pawl 98 to its disengaged position.

After a suitable period of time has elapsed, the dwelli timer 318 times out, closing the dwell timer switch 320.v The circuit is thus closed through the input wire 20, a lead wire 36, the head traverse up switch relay 324,. a lead wire 37, dwell timer switch 320, a lead Wire 38,. and return wire 21. The head traverse motor up switch 300 closes, causing the grinding head to be driven upwardly at the traverse rate to separate the grinding wheel. from the work. It will be understood that the electrical diagram above described is not complete and that only so much of the electrical connections of the machine are: shown as are believed necessary to illustrate the connec-- tion of the invention therewith. The control of the head; traverse motor, for example, to effect the automatic up and down rapid traverse movement of the grinding head; is shown only in part.

With the construction and arrangement shown in Fig. 9 an automatic control of the shift to slow speed is. effected by the engagement of the work engaging element. advancing at a controlled rate with the slow speed micr0 switch 280. The slow rate of advance of the work engaging element assures a reasonably accurate operation of the gauging device which will be aifected to only a slight extent by the continued downward movement of' the work engaging element into the voids between adjacent work-pieces. Fig. 10 illustrates an alternative ar rangement of the slow feed control mechanism which may be employed to cause the slow feed to start at a more precisely determined point in the progress of the grinding. operation. In the alternative form as shown in Fig. 10, the microswitch 280 is placed in a slow feed timer circuit which includes a lead-in wire 20, a connector 39, the solenoid 328 of a slow feed timer relay, a connector 40,. the micro-switch 280, connector 41, and return wire 21.

'11 The slow feed timer as shown in Fig; comprises with the solenoid 328 an armature 330, dash pot 332, slow feed timer switch 334,'and a'manually adjustably regulator 336. The operation of the slow feed timer is similar to the operation of the stop feed timer previously described in that the timer is not permitted to time out until the actuation of the slow feed microwitch 280 ceases to be intermittent and remains closed for a period in excess of that required for one revolution of the chuck 40. By reference to Fig. 3 it will readily be seen that while a movement of the work engaging element 206 beyond the slow feed position will cause switch arm 286 to be engaged and moved away from the slow feed micro-switch contact.

290 to close the switch a subsequent reverse movement of the work engaging element 206 upon engagement with any still oversize work surface will permit the switch arm 286 to return to its normally engaging position to open the slow feed micro-switch 280. Thus the slow feed micro-switch 280 will be permitted to remain in its closed position only after the work has been ground down to a predetermined size in which the work engaging element 206 is permitted to remain in an angular position which holds the switch arm 286 out of engagement with the slow feed micro-switch contact 290.

Assuming that the work has been ground down to the prefinish size for which the slow feed microswitch 280 is adjusted and that the micro-switch 280 is permitted to remain in its closed position, the slow feed dwell timer now times out following one revolution of the chuck 40. The timer switch 334 closes, energizing the slow feed solenoid circuit which, as shown in Fig. 10, comprises output wire 20, a connector 42, the slow feed timer switch 334, connector 43, a slow feed solenoid 140, connector 44, and return wire 21. The energizing of the slow feed solenoid 140 acts as above described to shift the block 128 into the path of pin 142 on the pawl lever, limiting the movement of the pawl to one tooth on the feed ratchet 86.

Fig. 11 of the drawings illustrates in modified form a work gauging device adapted for use with a surface grinding machine of the type described to provide a visual indication that the work has been ground to size. The modified form shown in Fig. 11 is also adapted for the automatic control of the grinding wheel feed in an automatic type grinder such as that illustrated, for example, in the U. S. patent to Spencer, No. 1,535,080. The indicating device as arranged to provide a visual indication that the work has been ground to size comprises specifically an electric lamp which produces an intermittent signal to correspond with the intermittent operation of the stop feed micro-switch, and a steady signal when the feed stop micro-switch remains closed to indicate that the work has been ground to size, and that it is therefore time for the operator to disengage the grinding feed of the machine. Referring specifically to Fig. 11, certain of the parts shown correspond with those previously described and illustrated and are therefore given the same number. These parts include the gauge unit housing 204 which is mounted in the manner described on the gauge arm 202 and provides support for a horizontally disposed rock shaft 248 which carries the work engaging element 206. The synchronous motor and friction gear driving mechanism shown in Pig. 3 have, however, been omitted. The pivot shaft 248 and work engaging element 206 are urged in a clockwise direction as viewed in Fig. 11 by means of a tension spring 340 connected at one end to a downwardly extending bracket 342 and at its other end to the wall of the housing 204. The stop screw 279 is arranged for engagement with the bracket 342 to limit the downward movement of the work engaging element 206 in a substantially perpendicular position with relation to the work surface of the chuck. When the work engaging element reaches the limiting position shown in Fig. 11, an upward extension 344 of the bracket is arranged to engage with a contact element 346 which forms part of a feed stop indicator micro-switch 348; The micro-switch 348tis connected into" anelectric' circuit which includes. a lead wire 350, an indicatorrlamp 352, a lead wire 354,'a battery 356, and a return lead wire 358.

The modification of applicants gauging device illustrated in Fig. 11 operates in the following manner. It is assumed that prior to the start of the grinding operation the gauging device has been set with the assistance of a master block to a position in which the work engaging element just clears the surface of the master block. During the grinding operation and while the workpieces mounted on the chuck are oversize the work engaging element will alternatively be moved to the right against the pressure of its spring 340 by engagement with the work surfaces, or will be moved rapidly down to the limiting position shown in Fig. 11 under the infiuence'of its spring when a void between the workpieces is encountered. So long as the work is oversize, a continued alternate opening and closing of the micro-switch 348 takes place, thus causing an intermittent indication by the lamp. When the work is reduced to precisely the desired size, the work engaging element 206 will remain at rest in the position'shown in Fig. 11 with the extension 344 engaged with the contact element of the micro-switch 348 so that the indicating lamp 352 remains on. The operator will now disconnect the power feed in the usual manner by raising the vertically disposed plunger 259, indicated in Fig; 7, which raises the pawl throw-out lever 148 to disengage the pawl 98 from the ratchet wheel 86 in the manner above described.

The modified form of the gauging device shown in Fig. 11 is also particularly adapted for automatic control of an automatic grinding operation of the type described in the patent to Spencer above referred to in which successive workpieces are ground to a predetermined size in a single pass beneath an end face grinding wheel and are then discharged from the machine. In such a machine the gauging device is arranged so that the finished workpieces will pass successively beneath the work engaging element 206 which is located at a precisely determined distance above the Work supporting surface of the magnetic chuck. In an automatic grinder of the type referred to, the grinding wheel is preset to grind the work to a predetermined thickness, and the gauging device is correspondingly set so that so long as work of the required thickness is produced, the successive workpieces pass successively beneath the gauge, barelygrazing but without disturbing the position of the work engaging element 206. However, as wear of the grinding Wheel takes place, there is a tendency for workpieces of slightly greater than normal thickness to be produced. The work engaging element 206 engaged by such oversize pieces is moved to the right from the position shown in Fig. 11, causing the microswitch 348 to open and a feeding movement of the grinding wheel toward the work to take place. As the successively produced workpieces are again brought down to the precise size, the work,

engaging element 206 returns to the position of Fig. 11, closing the micro-switch 348 which actsrto' arrest the grinding feed.

For the automatic control of the grinding feed in the manner described, the pawl and ratchet wheel feed shown in Fig. 7 and the relay circuit including the lead wire 31, switch 317, and stop solenoid 166 illustrated in Fig. 9 may be employed. It is further assumed that the rapid traverse up connections inclndingdwell timer relay 318 are disconnected. As shown in Fig. 11, the switch 317 is arranged to be acted upon by a solenoid 360 which is arranged to be connected in a closed circuit in series with the micro-switch 348 upon the closing of a manually operable selector switch 361. 'The arrangement of the solenoid 360, and switch 317 as shown in Fig. ll, is such that the closing of the micro-switch 348 energizes solenoid 360, which in turn closes the control stop switch 317 to energize stop solenoid 166, which causes the'feed pawl 98 to be disengaged. The movement of the work 13 engaging element 206 away from the micro-switch 348 when an oversize workpiece is encountered de-energizes relay 360, permitting control stop switch 317 to open so that the stop solenoid 166 is de-energized and the pawl 98 is permitted to drop into its operating position to effect a down feed of the grinding wheel.

Fig. 12 of the drawings illustrates a still further embodiment of the invention in which an actuating spring is employed in combination with a dash pot mechanism to obtain a yieldable feed of the work engaging element 205 against the ground work surface at a controlled rate, this construction being utilized in substantially the same manner as that illustrated in Fig. 11 to provide a visual indication that the work in the machine has been ground to size. Referring specifically to Fig. 12, the several parts are identical to those illustrated in Fig. 11 except that a dash pot 362 has been added, together with a modified form of bracket which is arranged to provide an operative connection with the dash pot. As shown in Fig. 12, the bracket comprises a downwardly extending member 364 which is clamped to the rock shaft 248 and arranged to be moved into engagement with the adjnstable stop pin 279 in the housing in order to limit the downward feed of the work engaging element. An upwardly extending arm 366 of the bracket is arranged to be brought into engagement with the contact element of the micro-switch 348 at the precise instant when the work engaging element 2% reaches its depth stop position. A horizontally extending arm 368 formed integrally with the bracket is arranged to overlie a plunger 370 of the dash pot 362, these parts being arranged so that the dash pot will resist and very substantially slow the movement of the several parts, including the work engaging element in the clockwise direction under the influence of its spring 340. The engagement of the extension 366 with the contact element of micro-switch 348 acts in the manner described in connection with Fig. 11 to light the signal lamp 352, to give an intermittent signal followed by a steady signal as the work is brought to size. The spring 340 and dash pot 362 are constructed and arranged to advance the work engaging element 266 at a rate which is somewhat in excess of the rate of stock removal. The oscillatory movements imparted to the work engaging element 206 are with this arrangement to a large extent damped out, and the efliciency of the gauging device measurably improved.

The invention having been described, what is claimed 1. In a surface grinding machine, a base, a rotatable work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a relative depth feeding movement to said supports of controlled extent for the removal of surplus stock from any workpiece disposed on said work supporting surface, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element movably supported on said support to move to a predetermined limit position on the support toward the work supporting face and further arranged and shaped to be retracted from said face by engagement with a workpiece on said face passing beneath the work engaging element, means moving the work engaging element yieldably against and beyond the surface of an oversized workpiece to said limit position toward the work supporting face, an actuating element on the gauge support actuated by movement of the work engaging element to said predetermined limit position having an alternate response to said movements of the work engaging element to and retracting movements away from said position and a steady response to the continued engagement of the work engaging ele- I4 ment in said position, and a signal device controlled by said actuating element to signal the change from alternating to a steady response of said actuating element.

2. In a surface grinding machine, a base, a rotatable work support with a fiat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a rela= tive depth feeding movement to said supports of controlled extent for the removal of surplus stock from any workpiece disposed on said work supporting surface, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element movably supported on said support to move to a predetermined limit position on the support toward the work supporting face and further arranged and shaped to be retracted from said face by engagement with a workpiece on said face passing beneath the work engaging element, means moving the work engaging element yieldably toward the work supporting face, an actuating element on the gauge support actuated by movement of the work engaging element to said predetermined limit position having an alternate response to said movements of the work engaging element to and away from said position and a steady response to the continued engagement of the work engaging element in said position, a timing device rendered operative by said response of the actuating element and permitted to time out only after a predetermined period of steady response, and a control element actuated by said timing device upon completion of the timing out period.

3. in a surface grinding machine, a base, a work support with a fiat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting relative traversing and relative depth feeding movements to said supports of controlled extent for the removal of surplus stock from any workpiece disposed on said work supporting surface, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said Work supporting face and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular position approaching the vertical with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means moving said work engaging element yieldably along said path in a direction opposed to the direction of movement of said portion of the work supporting face against and beyond the depth of an oversized workpiece mounted on said face to said predetermined angular position, means on the gauge support to arrest movement of the work engaging element in said predetermined angular position, and an actuating element arranged to be rendered operative by the advance of said work engaging element to said predetermined angular position along said path and inoperative by a movment of the work engaging element away from said position.

4. A work gauging device for a surface grinding machine having a rotatable work support with a fiat work supporting face, a grinding wheel, a grinding wheel support, and means for imparting a rotary movement to said work support and relative depth feeding movement to said supports for the removal of surplus stock from any workpiece disposed on said work supporting surface, which comprises a gauge support on the machine disposed over said work supporting face and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said Work engaging surface toa predetermined angular limit position on the gauge support approaching the vertical with relation to the work supporting face along a path and in a direction opposed to the direction of movement of that portion of the work supporting face passing beneath said element against and beyond the depth of an oversized workpiece mounted on said face to said predetermined angular position, means moving said work engaging element yieldably along said path in a direction opposed to the direction of movement of said portion of the work supporting face, an actuating element on the gauge support having an alternate response to the movement of said work engaging element to and from said limit position and a steady response to'the continued engagement of the work engaging element in said predetermined position, and an indicating device constructed and arranged to indicate selectively the intermittent and steadyresponse of said actuating element.

5. A work gauging device for a surface grinding machine having a rotatable work support with a flat work supporting face, a grinding wheel, a grinding wheel support, and means for imparting a rotary movement to said work support and a relative depth feeding movement for the removal of surplus stock from any workpiece disposed on said work supporting face, which comprises a gauge support on the machine disposed over said work supporting face and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a limit position approaching substantially the vertical with relation to a moving portion of the work supporting face traversed by said work engaging element along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means moving said work engaging element yieldably along said path in a direction opposed to the direction of movement of said portion of the work supporting face tending to move said work engaging element against and beyond the depth of an oversized workpiece to said limit position, means on the gauge support to arrest movement of the work engaging element in said limit position, and an actuating element on the gauge support actuated by movement of the work engaging element to said limit position on said gauge support toward the work face having an alternate response to said movements of the work engaging element to and from said limit position and a steady response to the engagement of the work engaging element in said position.

6. A work gauging device for a surface grinding machine having a rotatable work support with a flat work supporting face, a grinding wheel, a grinding wheel support and means for imparting a rotary movement to said work support and a relative depth feeding movement to said supports for the removal of surplus stock from any workpiece disposed on said work supporting surface, which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a substantially perpendicular limit position with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means urging the work engaging element against the ground surface of the work along said path in a direction opposed to the direction of movement of said portion of the work supporting face yieldably at a controlled rate having a component of movement toward the work supporting face at a rate which is in excess of the rate of stock removal, an actuating element having a response to the engagement of said work engaging element in said predetermined angular position and an alternate response to a retracting movement of the work engaging element from said position, a timing device having a timing out period rendered operative by the response of'the actuating element to start timing out and rendered inoperative by an alternate response prior to the timing out of said timing device, and a control element actuated by said timing device only upon completion of said timing out period. 7 7 a 7. In a surface grinding machine, a base, a rotatable work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for im parting a rotary movement to said work support and a relative depth feeding movement to said supports of controlled extent for the removal of surplus stock from any workpiece disposed on said 'work supporting face, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward the work supporting face to a predetermined angular position along a path and in a direction opposed to the direction of movement of that portion of the work supporting face passing beneath said element, means moving the work engaging element yieldably along said path toward the work supporting face, an actuating element having a response to the engagement of said work engaging element in said predetermined position and an alternate response to a retracting movement of the work engaging element from said position, a timing device having a timing out period rendered operative by the response of the actuating element to start timing out and rendered inoperative by an alternate response of said actuating element during said timing out period, and control means actuated by said timing device only upon completion of said timing out period to control said relative depth feeding movement.

8. In a surface grinding machine, a base, a rotatable work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a relative depth feeding movement to said supports at a feed and thereafter at a slow feed rate for the removal of surplus stock from any workpiece disposed on said work supporting face, means for shifting to a slow rate and for stopping said relative depth feeding movement of said supports, and a gauging device which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting surface to a substantially perpendicular limit stop position with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the Work supprting face, means urging the work engaging element against the ground surface of the work yieldably at a controlled rate having a component of movement toward the work supporting face at a rate which is in excess of the rate of stock removal, a slow feed actuating element on the gauge support actuated by movement of the work engaging element to a predetermined position toward said limit stop position to render operative said slow feed shifting means, a feed stop actuating element on the gauge support actuated by movement of the work engaging element to said limit stop position having a response to movement of the actuating element and an alternate response to a retracting movement away from said position and a steady response to the continued engagement of the actuating element in said position, and means actuated by a change from an alternate to a steady response of said feed stop actuating element to render operative said means to stop the relative depth feed.

9. In a surface grinding machine, a base, a rotatable work support with a fiat work supporting face mounted from the base, a grinding Wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a relative depth feeding movement to said supports for the removal of surplus stock from any workpiece disposed on said work supporting face, electrically operated eans for controlling said relative depth feeding movement, and a gauging device gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular limit position along a path and in a direction opposed to the direction of movement of that portion'of the work supporting face passing beneath said element, means moving they work engaging element yieldably toward the Work supporting face, a switch arranged to be actuated upon movement of the work engaging element to said limit position and to be inactivated by a retractin movement of the work engaging element away from said position, a time delay device comprising a time delay relay connected to be energized by said switch, and electrically operated means responsive to the operation of said switch upon the timing out of the time delay device to control said relative depth feeding movement.

10. A gauge for use in a surface grinding machine having a base, a wor; support with a flat work supportingface mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to efiect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said face, which comprises a gauge support on the machine disposed over said work engaging surface and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular position toward the vertical with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means biasing the work engaging element yieldably along said path toward the work supporting face against and beyond the depth of an oversized workpiece mounted on said face to said predetermined angular position, means acting to retard the advance of the work engaging element under the influence of said biasing means whereby the work engaging element is advanced yieldably at a controlled rate, an actuating element on the gauge support actuated by movement of the work engaging element to said predetermined position having a response to said movement of the work engaging element to said position and an alternate response to the movement of the work engaging element away from said position and a steady response to the continued engagement of the work engaging element in said position, and a signal device controlled by the responses of said actuating element to signal a change from an alternating to a steady response of said actuating element.

11. A gauge for use in a surface grinding machine having a base, a work support with a flat work supporting face mounted from the base, a grinding Wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said surface, which comprises a gauge support on the machine disposed over said work engaging surface,

a Work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular position with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means urging the work engaging element toward the work supporting face at a controlled rate comprising a driving member on the gauge support, means for driving said member at a predetermined rate, a, friction driving connection between the driving member and work engaging element, and an actuating element on the gauge support arranged to be actuated by the WOIk, engaging element upon movement thereof to said limit position.

12. A gauge for use in a surface grinding machine hav ing a base, a work support with a flat Work supportingface mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports beirv constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said surface, which comprises a gauge support on the machine disposed over said work engaging surface, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular position with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, an actuating element on the gauge support actuated by movement of the work engaging element to said predetermined angular position toward the work face, means urging the work engaging element along saidv path at a controlled rate having a component of movement against the work face at a rate in excess of the rate of stock re,- rnoval including a rotatable driving member loose on said pivot, means for driving said member at a predetermined rate, and a friction driving connection between the drivmember and said work engaging element.

13. A gauge for use in a surface grinding machine having a base, a work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding Wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding Wheel across the face of the work support and av depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said face, which comprises a gauge support on the machine disposed over said work engaging surface, a work engaging element, a pivot, shaft on the support on which the work engaging element is mountedfor a limited movement radially from the pivot shaft, and for turning movement toward the work face to a substantially vertical limit position with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means yieldably supporting said work engaging element in an extended radial position from the pivot shaft, means yieldably rotating the pivot shaft and work engaging element toward the work face at a controlled rate having a component of movement toward the work face at a rate in excess of the rate of stock removal, and an actuating element on the gauge support arranged to be actuated by the work engaging element upon movement thereof to said limit position.

14. A gauge for use in a surface grinding machine having a base, a work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding Wheel toward said face for the removal of surplus stock from any workpiece disposed on said face, which comprises a gauge support on the machine disposed over said work engaging surface, a work engaging element, a pivot shaft on the support on which the Work engaging element is supported to rotate toward the work supporting face to a predetermined angular position with relation to the moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, a driving member loose on said pivot shaft, an axially preloaded ball bearing connection between the driving member and the pivot shaft providing a light friction driving connection between the shaft and element, means for driving said driving member continuously at a constant rate and in a direction to urge the work engaging element along said path toward the work supporting face, and an actuating element on the gauge support arranged to be actuated by the work engaging element upon movement thereof to said predetermined position.

, 15. A gauge for use in a surface grinding machine having a base, a work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding Wheel mounted from the base, said supports being constructed and arranged for relative movements to eifect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said surface, which comprises a gauge support on the machine disposed over said work engaging surface, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular position along a path and in a direction opposed to the direction of movement of that portion of the work supporting face passing beneath said element, a driver rotatably supported on the gauge support, means for continuously rotating the driver, a preloaded ball bearing connection between the driver and the work engaging element providing a light friction driving connection therebetween, an actuating element on the gauge support arranged to be actuated by the work engaging element upon movement thereof to said predetermined angular position, and a signal device rendered operative by the response of said actuating element.

16. A gauge for use in a surface grinding machine having a base, a work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said surface, which comprises a gauge support on the machine disposed over said work engaging surface, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular limit position along a path and in a direction opposed to the direction of movement of that portion of the work supporting face passing beneath said element, a driver rotatably mounted on the gauge support, an axially preloaded ball bearing connection between the driving mem ber and the pivot shaft providing a frictional driving resistance between the shaft and the element in the order of two ounces applied tangentially to the work engaging portion of said element, a synchronous motor connected I to drive the driver and work engaging element therewith at a rate having a'component of movement toward the work face in excess of the rate of stock removal, and an actuating element on the gauge support arranged to be actuated by the work engaging element upon movement thereof to said predetermined angular position.

17. A gauge for use in a surface grinding machine having a base, a work support with a fiat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said surface, which comprises a gauge support arranged to be supported on the machine over said work engaging surface, a work engaging element, a pivot shaft on the support on which the work engaging element is supported to rotate to a predetermined angular position with rela tion to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means urging the work engaging element toward the work face ata controlled rate comprising a driving member loose on the pivot shaft, a pair of ball bearings carried on the pivot shaft at each side of the driving member and spring means axially preloading said ball bearings between the shaft and said driver to provide a light friction driving connection between the shaft and driver, means for driving said driving member continuously at a predetermined rate, and an actuating element on the gauge support arranged to be actuated by movement of the work engaging element to a predetermined position.

18. A gauge for use in a surface grinding machine having a base, a work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said surface, which comprises a gauge support arranged to be supported on the machine over said work engaging surface, a work engaging element, a pivot shaft on the support on which the work engaging element is supported to rotate to a predetermined angular position with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means urging the work engaging element toward the work face at a controlled rate comprising a driving member. loose on the pivot shaft, a ball bearing having an externai and an internal race mounted on the pivot shaft at each side of the driving member, and with only the external races thereof engaging the driving member, spring means on the pivot shaft acting axially against the internal races of said bearings to preload the bearings axially against the driver, a synchronous motor connected with the driving member for continuously driving said member at a predetermined rate, and an actuating means on the gauge support responsive to movement of the work engaging element to a predetermined angular position.

19. In a surface grinding machine, a base, a work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the face of the work and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said face, operating and control devices for the machine including electrically operated means for automatically arresting said relative depth feeding movement of said supports, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a substantially vertical limit position along a path and in a direction opposed to the direction of movement of that portion of the work supporting face passing beneath said element, means moving the work engaging element yieldably toward the work supporting face, a switch having an alternate response to the movement of the work engaging element to and from said limit position, a time delay device comprising a time delay relay connected to be energized by said switch upon movement of the work engaging element to the limit position, electrically operated means responsive to the operation of said switch upon the timing out of the time delay device to control the relative depth feeding movement, and a visual indicating device connected to be operated by said switch.

20. The method of sizing work dispersed on the work supporting face of the work support of a surface grinding machine having a work support and grinding wheel support constructed and arranged for relative movements to efiect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face, and a gauging device comprising a gauge support on the machine disposed over said work engaging surface, and a Work engaging element pivoted on the gauge support for movement toward said work supporting face to a limit position approaching the vertical with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, which comprises the steps of moving said work engaging element yieldably along said path against and beyond the depth of an oversized workpiece mounted on said face to said limit position whereby the work engaging element is given successive impulses away from said limit position by oversize workpieces, sensing the change between alternating movements of the work engaging element to and away from said limit position and the continued location of the work engaging element in said limit position, and utilizing said change to control the machine operation.

21. In a surface grinding machine, a base, a rotatable work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a relative depth feeding movement to said supports of controlled extent for the removal of surplus stock from any workpiece disposed on said work supporting face, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, a Work engaging element movably supported on said support to move toward the work supporting face and further arranged and shaped to be retracted from said face by engagement with a workpiece on said face passing beneath the work engaging element, means moving the work engaging element yieldably toward the work supporting face, an actuating element on the gauge support actuated by movement of the work engaging element to a predetermined advanced position on said gauge support toward the work face having a limit and away-from-limit response to said movement of the work engaging element to and retracting movements away from said position and a steady limit response to the continuing engagement of the work engaging element in said position, a work feed control element, and a device responsive to said limit response of the actuating element and acting after a delay period to actuate said work feed control element, and responsive to said away-from-limit response during said delay period to render said device inoperative.

22. In a surface grinding machine, a base, a rotatable work support with a fiat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a relative depth feeding movement to said supports of controlled extent for the removal of surplus stock from any workpiece disposed on said work supporting surface, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element movably supported on said gauge support to move to a predetermined advanced position toward the work supporting face and further arranged and shaped to be retracted from said face by engagement with workpiece on said face passing beneath the work engaging element, means moving the work engaging element yieldably against and beyond the surface of an oversized workpiece to said predetermined advanced position toward the work supporting face at a controlled rate which tends to be in excess of the rate of stock removal, an actuating element on the gauge support actuated by movement of the work engaging element to a predetermined advanced position on said gauge support toward the work face, a work feed control element, and a timing device responsive only to the uninterrupted actuation of said actuating element thru a dwell period to arrest the relative depth feeding movement of said supports and actuate said work feed control element and thereby to arrest the relative depth feeding movements of said supports.

23. A work gauging device for a surface grinding machine having a work support with a flat work supporting face, a grinding wheel, a grinding wheel support, and means for imparting relative traversing movements and relative depth feeding movements to said supports for the removal of surplus stock from any workpiece disposed on said Work supporting surface, which comprises a gauge support on the machine disposed over said work supporting face, and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work engagin surface to a predetermined angular position approaching the vertical on the gauge support along a path and in a direction opposed to the direction ofmovement of that portion of the work supporting face passing beneath said element, against and beyond the depth of an oversized workpiece mounted on said face to said predetermined angular position, means moving said work engaging element yieldably along said path in a direction opposed to the direction of movement of said portion of the work supporting face, and an actuating element on the gauge support having an alternate response to the movement of said work engaging element to and from said predetermined position and a steady response to the continued engagement of the work engaging element in said predetermined position, a work feed control element, and a timing device rendered operative by said response of the actuating element and permitted to time out only after a predetermined period of steady response to actuate the work feed control element.

24. In a surface grinding machine, a base, a rotatable work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a relative depth feeding movement to said supports of controlled extent for the removal of surplus stock from any workpiece disposed on said work supporting face, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a limit position approaching the vertical with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means moving said work engaging element yieldably along said path in a direction opposed to the direction of movement of said port on of the work supporting face against and beyond the depth of an oversized workpiece mounted on said face to said predetermined angular position, means on the gauge support to arrest movement of the work engaging element in said substantially vertical limit position, an actuating element arranged to be rendered operative by the advance of said work engaging element to said position, a work feed control element, and a timing device actuated by said actuating element and permitted to time out only after a period of continued rest of said actuating element in said limit position to actuate the work feed control element.

25. A work gauging device for a surface grinding machine having a rotatable work support with a flat work supporting face, a grinding wheel, a grinding wheel support, and a means for imparting a rotary movement to said work support and a relative depth feeding movement for flue removal of surplus stock from any workpiece disposed on said work supporting face, which comprises a gauge support on the machine disposed over said work supporting face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a limit position approaching the vertical with relation to a moving portion of the work supporting face and having a pro vision for a depth feed adjustment toward and away from said face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means urging the work engaging element against the ground surface of the work along said path in a direction opposed to the direction of movement of said portion of the work supporting face yieldably at a controlled rate having a component of movement toward the work supporting face at a rate which is in excess of the rate of stock removal against and beyond the depth of an oversized workpiece mounted on said face to said limit position, an actuating element on the gauge support actuated by the movement of the work engaging element to a predetermined advanced position on said gauge support toward the work face, a work feed control element, and a timing device actuated by said actuating element and permitted to time out only after a period of continued rest of said actuating element in said advanced position to actuate the work feed control element.

26. A work gauging device for a surface grinding machine, having a rotatable work support with a flat work supporting face, a grinding wheel, a grinding wheel support and means for imparting a rotary movement to said work support and a relative depth feeding movement to said supports for the removal of surplus stock from any workpiece disposed on said work supporting surface, which comprises a gauge support on the machine disposed over said work supporting face and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting surface to a limit stop position approaching the vertical with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means urging the work engaging element against the ground surface of the work along said path in a direction opposed to the direction of movement of said portion of the work supporting face yieldably at a controlled rate having a component of movement toward the work supporting face against and beyond the depth of an oversized workpiece mounted on said face to said limit stop position at a rate which is in excess of the rate of stock removal, an actuating element on the gauge support actuated by movement of the Work engaging element to said limit stop position having an alternate response to movement of the actuating element to' and a retracting movement away from said position, and a steady response to the continued engagement of the actuating element in said position, a work feed control element, and a timing device rendered operative by said response of the actuating element and permitted to time out only after a predetermined period of steady response to actuate the work feed control element.

27. in a surface grinding machine, a base, a rotatable work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a relative depth feeding movement to said supports .of controlled extent for the removal of surplus stock from any workpiece disposed on said work supporting face, means for controlling said relative depth feeding movement, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular position along a path and in a direc= tion opposed to the direction of movement of that portion of the work supporting face passing beneath said element, means moving the work engaging element yieldably along said path forward against the work supporting face, against and beyond the depth of an oversized workpiece mounted on said face to said predetermined angular position, a switch arranged to be closed upon movement of the work engaging element to said predetermined position and to be opened by the retracting movement of the work engaging element away from said position, an electrically operated signal device connected to give one response to the closing of said switch and another response to the opening of said switch, and electrically operated means having a timing period extending through at least one revolution of the work support for actuating said depth feed control means, and responsive to the closing of the switch to start said timing period, and responsive to the opening of said switch to discontinue said timing period.

28. In a surface grinding machine, a base, a rotatable work support with a fiat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, means operable for imparting a rotary movement to said work support and a relative depth feeding movement to said supports of controlled extent for the removal of surplus stock from any workpiece disposed on said work supporting surface, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation,

which comprises a gauge support on the machine disposed over said work supporting face, and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular limit position toward the vertical with relation to a moving portion of the work supporting face along a path and in a direction opposed to the direction of movement of that portion of the work supporting face excess of the rate of stock removal, and an actuating element on the gauge support actuated by movement of the work supporting engaging element to said limit position toward the work supporting face having an alternate response to said movements of the work engaging element to and retracting movements away from said position and a steady response to the continued engagement of the work engaging element in said position, and a control element rendered operative only by a continued steady response of said actuating element through one revolution of the work support.

29. A gauge for use in a surface grinding machine having a base, a work support with a flat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the face of the work support and a depth feeding movement of the grinding wheel toward said face for the removal of surplus stock from any workpiece disposed on said face, which comprises a gauge support on the machine disposed over said work engaging surface, and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a predetermined angular position toward the vertical with relation to a moving portion of the Work supporting face along a path and in a direction opposed to the direction of movement of said portion of the work supporting face, means biasing the Work engaging element yieldably along said path toward the work supporting face, against and beyond the depth of an oversized workpiece mounted on said face to said predetermined angular position, means acting to retard the advance of the Work engaging element under the influence of said biasing means whereby the work engaging element is advanced yieldably at a controlled rate, and an actuating element on the gauge support arranged to be actuated by the work engaging element upon continued engagement thereof in said predetermined position during the traversing movement of the grinding Wheel across the face of the work support.

30. In a surface grinding machine, a base, a work support with a fiat work supporting face mounted from the base, a grinding wheel support and a grinding wheel mounted from the base, said supports being constructed and arranged for relative movements to effect a traversing movement of the grinding wheel across the work supporting face and a depth feeding movement of the grinding Wheel toward said face for the removal of surplus stock from any workpiece disposed on said face, operat- 26 ing and control devices for the machine including means for automatically arresting said relative depth feeding movement of said supports, and a gauging device for gauging the work thickness during the progress of said surplus stock removal operation, which comprises a gauge support on the machine disposed over said work supporting face, and having provision for a depth feed adjustment toward and away from said face, a work engaging element, a pivot on the gauge support on which the work engaging element is rotatable toward said work supporting face to a limit position approaching the vertical with relation to said Work supporting face along a part and in a direction opposed to the direction of movement of that portion of the work supporting face passing beneath said element, means moving the work engaging element yieldably toward the work supporting face against and beyond the surface of an oversized workpiece mounted on said face to said limit position, an actuating element on the gauge support actuated by movement of the work engaging element to said limit position having an alternate response to alternate movements of the work engaging element to and from said position and a steady response to the continued engagement of the work engaging element in said position, a device having a timing period for actuating said means for automatically arresting said relative depth feeding movement of the supports, said device being constructed and arranged to be actuated only by a steady response of said actuating element through said timing period, and to be rendered inoperative by the interruption of an alternate response during said period, and a signal device controlled by said actuating element to give a visual indication distinguishing each of said alternate and steady responses of said actuating element.

References Cited in the file of this patent UNITED STATES PATENTS 915,174 Hanson Mar. 16, 1909 940,929 Hanson Nov. 23, 1909 1,198,772 Roach Sept. 19, 1916 1,349,222 Olsson Aug. 10, 1920 1,436,674 Olsson Nov. 28, 1922 1,535,080 Spencer Apr. 21, 1925 1,835,459 Brittain Dec. 8, 1931 1,923,762 Stevens Aug. 22, 1933 1,982,161 Gurney Nov. 27, 1934 2,008,137 Gurney July 16, 1935 2,148,744 Hall Feb. 28, 1939 2,372,824 Gould Apr. 3, 1945 2,419,133 Garside Apr. 15, 1947 

